Methods and apparatus for transferring electrical components

ABSTRACT

A mechanism for handling semiconductor wafers includes a feed section which comprises a vertically movable elevator able to hold a number of vertically spaced carriers. Each carrier has a film frame mounted thereon for supporting a wafer. A pulling mechanism pulls a selected carrier out of the elevator along a first axis and into a pick and place section. A transfer mechanism removes individual dies from the wafer and moves them to a flip station along a second axis oriented perpendicularly to the first axis. The transfer mechanism can move different distances along the second axis to be able to remove dies arranged in a row along the second axis. The flip station is driven by a single motor to both lower and invert the dies.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to the transfer of electrical components and in particular to methods and apparatus for handling semiconductor wafers, particularly the removal of individual dies from semiconductor wafers and a transferring of such dies.

[0003] 2. Description of Related Art

[0004] In the manufacture of electrical devices, it is conventional to pre-cut a semiconductor wafer into rows of individual components called “dies.” The dies are then individually removed and transferred for assembly into a chip package or multi-chip module.

[0005] It is conventional to perform such die removal and transfer operations by an automated machine. Such a machine can include a wafer feed section where a plurality of wafers are stored, a pick and place section for transferring individual dies from the wafers, and a receiver section in the form of a flip station which receives and inverts the dies.

[0006] At the feed section each wafer is adhesively mounted on a film that is fixed to a ring-shaped film frame or holder, with the film extending across an aperture formed in the film frame. A circular ring may be placed on the film in surrounding relationship to the wafer, to keep the film taut.

[0007] The wafer feed section can include a vertically movable elevator, with the film frames seated horizontally in vertically spaced relationship within slots formed in opposing walls of the elevator. By raising or lowering the elevator, a particular film frame can be brought into horizontal alignment with a slidable pulling device which is able to couple itself to a film frame to pull the film frame from the elevator along a first linear path or axis.

[0008] A transfer mechanism is provided at the pick and place section for transferring individual dies from the wafer. The transfer mechanism includes a vacuum pick head assembly and a die eject chuck. The vacuum pick head assembly includes a vacuum spindle arranged to grip a top face of a die by means of a suction force. The die eject chuck is arranged for pushing upwardly against the film at a location beneath the respective die, in order to raise that die relative to the other dies of the wafer. The chuck includes one or more ejector needles which move upwardly relative to the chuck after the die has been raised by the chuck, in order to assist in separating the die from the tape. The pick head assembly then travels along a second linear path or axis oriented perpendicularly to the first axis to deposit the die at the receiver section and then returns along the second axis to pick up another die from the wafer.

[0009] The pick head assembly travels a constant distance along the second axis. Thus, since the dies are in arranged rows, with each row lying along the second axis, it is necessary, following the pick-up of each die, to index the film frame along the second axis in order to bring the next die into a position to be picked up by the vacuum spindle. Thus, the apparatus for displacing the film frame must be capable of displacing the film frame along dual axes.

[0010] Since wafers and dies are not of uniform size, it may be necessary to change to a larger or smaller vacuum spindle tip when picking up larger or smaller dies.

[0011] A mechanism can be provided to enable the vacuum spindle tip to be automatically replaced by tips of different size. An example of such a mechanism is described, for example in U.S. Pat. No. 5,105,528. A chuck replacement mechanism can also be provided in order to enable the eject mechanism to eject dies of different size. In such a chuck replacement mechanism, a number of differently sized die eject chucks are mounted on a rotary touret whereby a die eject chuck of suitable size can be indexed into an operative position by rotating the touret.

[0012] In some instances, the dies of the wafer are provided with solder bumps on their upwardly facing surfaces. Such so-called bump dies must be inverted before being placed on a package or module being manufactured. One manner of achieving that result is to have the pick head transfer the dies to a receiver section in the form of a flip mechanism which is able to lower and invert the dies by 180 degrees. One known flip mechanism employs a first motor for rotating a die receiving platform by 180 degrees and a second motor for moving the die receiving platform up and down.

[0013] Although the above-described apparatus has operated successfully, room for improvement remains. For example, the elevator accepts only one size of film frame, which means that wafers of different size cannot be simultaneously accommodated in the machine. As a result, a machine utilizing such an elevator cannot easily switch from one size wafer to another size wafer in order to manufacture a package or module with different types of dies. It would be desirable to be able to do so in a machine that utilizes an elevator for storing wafers.

[0014] It would also be desirable to simplify the machine by eliminating the dual-axis movement of the mechanism that moves and positions the film frames.

[0015] It would also be desirable from the standpoint of minimizing cost and complexity to enable different size die eject chucks to be selectively brought into operative position without having to move the die eject chucks.

[0016] Yet another area which results in extra complexity and cost is the provision of two motors for operating the flip mechanism. It would be desirable to simplify that device by eliminating one of the motors.

SUMMARY

[0017] One aspect of the present invention relates to a wafer handling apparatus which comprises a frame structure, a holder displacement mechanism, and a transfer mechanism. The frame structure comprises a wafer feed section, a wafer pick and place section, and a wafer receiving section. The wafer feed section stores a wafer holder which is adapted to support a wafer comprised of precut dies. The wafer pick and place section is spaced from the wafer feed section along a first axis. The wafer receiving section is spaced from the wafer pick and place section along a second axis which crosses the first axis. The holder displacement mechanism is arranged for movement between the feed section and the pick and place section for transferring a wafer holder from the feed section to the pick and place section linearly along the first axis. The transfer mechanism is arranged for movement between the pick and place section and the receiving section for picking up and transferring wafer dies from the pick and place section to the receiving section linearly along the second axis. The transfer mechanism is movable by different distances along the second axis for picking up dies arranged adjacent one another along the second axis.

[0018] Another aspect of the invention relates to carriers adapted to carry film frames which support precut semiconductor wafers. The carrier comprises a plate having a hole extending therethrough, and a recess formed adjacent one end of the plate. The recess is disposed parallel to the plate and opens towards the hole. The recess is adapted to receive part of a film frame. A plurality of removable positioning pins extend into the recess and are adapted to mate with positioning notches formed in a film frame. A hold-down structure is mounted on the plate adjacent a side of the hole disposed opposite the recess, for holding a portion of a film frame.

[0019] Yet another aspect of the invention relates to a method of feeding semiconductor wafers which comprises the steps of:

[0020] A. seating the wafers on respective film frames, each film frame having an aperture and a film extending across the aperture for supporting the respective wafer, the apertures of at least some of the film frames being of different size from the apertures of others of the film frames;

[0021] B. mounting the film frames on respective carriers, each carrier having a hole sized in accordance with the size of the aperture of the respective film frame, the hole of each carrier being aligned with the aperture of the respective film frame;

[0022] C. positioning the carriers in vertically spaced relationship in respective support seats of a vertically movable elevator, each of the carriers configured to be received in any of the support seats; and

[0023] D. selectively raising and lowering the elevator to bring a selected carrier to an elevation suitable for being removed from the elevator.

[0024] Yet another aspect of the invention relates to a wafer feeder which comprises a mainframe, a wafer holder, a die flip station, a pick-up head, and a control means. The wafer holder is adapted to support a wafer which includes a plurality of precut dies. The die flip station includes a track, a pivotable platform slidably mounted on the track, and a drive mechanism. The die flip station is mounted adjacent the wafer holder. The pick-up head is located so as to pick up a die from the wafer and drop the die onto the pivotable platform of the die flip station. The control means controls the die flip station so as to pivot the pivotable platform whereby the die can be dropped from the pivotable platform onto an adjacent surface. The die flip station includes a belt drive connecting the drive mechanism to the pivotable platform. The belt drive includes means for pivoting the pivotable platform and for moving the pivotable platform linearly along the track.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The objects and advantages of the invention will become apparent from the following detailed description of preferred embodiments thereof in connection with the accompanying drawings in which like numerals designate like elements and in which:

[0026]FIG. 1 is a top front perspective view of a wafer handling apparatus according to the present invention;

[0027]FIG. 2 is a side elevational view of the apparatus depicted in FIG. 1;

[0028]FIG. 3 is a rear elevational view of the apparatus depicted in FIG. 1;

[0029]FIG. 4 is a top perspective view of a film frame according to the present invention;

[0030]FIG. 5 is a top perspective view of a film frame carrier according to the present invention;

[0031]FIG. 6 is a top plan view of the film frame carrier with a film frame mounted thereon;

[0032]FIG. 7 is a top perspective view of a pulling head according to the present invention;

[0033]FIG. 8 is a top plan view of the film frame carrier carrying a film frame, and engaged by the pulling head of FIG. 7;

[0034]FIG. 9 is a side view of a flip station according to the present invention;

[0035]FIG. 10 is a front view of a flip station according to the present invention;

[0036] FIGS. 11(a) through 11(d) show an operation sequence of the flip station;

[0037]FIG. 12 is a perspective view of an embodiment of the present invention with some elements removed to show interior portions;

[0038]FIG. 13 is a back view of an embodiment of the present invention with some elements removed to show interior portions;

[0039]FIG. 14 is a perspective view of an embodiment of a vacuum pick head assembly of the present invention;

[0040]FIG. 15 is a side view of an embodiment of a vacuum pick head assembly of the present invention;

[0041]FIG. 16 is a perspective view of an embodiment of a die eject chuck assembly of the present invention; and

[0042]FIG. 17 is a side view of an embodiment of a die eject chuck assembly of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0043] An apparatus for removing individual dies from a semiconductor wafer comprises a wafer feed section A in which a plurality of wafers are provided, a pick and place section B where individual dies are removed from the wafers, and a receiver section C where the removed dies are deposited for further handling.

[0044] Wafer Feed Section

[0045] The wafer feed section A comprises a stationary base frame 102 to which an elevator 104 is mounted for up/down movement (see FIG. 3). The elevator includes a pair of parallel vertical side walls 106 of identical configuration. The side walls are interconnected by top and bottom walls 108, 110 to form a rigid structure.

[0046] Each side wall 106 includes an inner surface in which are formed a plurality of parallel, horizontally extending slots 112 or 112′ spaced equidistantly apart in the vertical direction. The slots 112 on one side wall are horizontally aligned with, and arranged parallel to, respective ones of the slots 112′ formed on the other side wall to form cooperating pairs of slots 112, 112′. Each pair of slots defines a support seat for supporting a wafer-carrying structure, as will be explained.

[0047] The elevator is raised and lowered by a drive mechanism 114 which comprises a vertically oriented lead screw 116 mounted within fixed bearings 118 for rotation about a vertical axis (see FIG. 1). The lead screw 116 meshes with a ball nut 120 fixed to a downwardly depending wall 121 of a carrier 111 on which the elevator bottom wall 110 is mounted, whereby rotation of the lead screw produces vertical movement of the elevator in an up or down direction, depending on the direction of rotation of the lead screw. Rotation of the lead screw is effected by a reversible electric motor 122 which drives the lead screw through a belt 124.

[0048] The elevator is adapted to carry semiconductor wafers, each of which is mounted on a ring-shaped film frame 162, shown in FIG. 4, on which a film or tape 164 is affixed in a conventional manner so as to extend across an aperture 165 formed by the film frame. A circular ring 163 can be placed on the film 164 in surrounding relationship to the wafer (not shown) for holding the film taut, as is conventional. An adhesive side of the film faces upwardly and is adhered to the undersides of the wafer dies. The film frame 162 is shaped and sized to fit onto a wafer carrier 166 which comprises a plate 168 having a hole 170 extending therethrough (see FIG. 5). The film frame 162 is larger than the hole 170, whereby the film frame can be seated on the carrier 166 with its aperture 165 disposed in overlying relationship to the hole 170.

[0049] The carrier includes positioning elements in the form of vertical pins 172 removably mounted in respective holes 173 formed in an attachment 174 secured to the plate 168. The attachment, together with the plate 168, forms a recess 176 into which a portion of the outer periphery of the film frame 162 can be slid, as shown in FIG. 6. The recess is disposed parallel to the plate 168 and opens toward the hole 170. The pins 172 extend into the recess.

[0050] The film frame 162 includes a positioning structure cooperating with the pins 172 for ensuring that the film frame can be properly oriented relative to the carrier 166. That positioning structure includes a pair of notches 178 arranged in a portion of an outer peripheral edge of the film frame which extends into the recess 176. Those notches are arranged to mate with respective pins 172. Hold-down elements in the form of spring clips 180 are mounted on the carrier to hold down a portion of the film frame 162 situated to a side of the hole 170 opposite the notches 178.

[0051] The pin/notch arrangement 172, 178 is used in cases where the wafer is mounted on the film in a predetermined orientation relative to the film frame, whereby a particular orientation of the wafer relative to the carrier 166 is automatically achieved when the pins 172 are seated within the notches 178.

[0052] However, in cases where the wafer is not in a specific orientation relative to the film frame, the pins 172 are not used. That is, the pins are removed from the holes 173, enabling the film frame 162 and wafer to be rotated to a suitable orientation relative to the carrier 166 before the spring clips 180 are swung into clamping position.

[0053] As noted earlier, each carrier 166 carries one film frame. Film frames which carry different size wafers may be of different sizes. For that reason, it was heretofore not possible to provide a variety of wafers in the elevator, since the slots 112, 112 each cooperating pair of slots in the elevator are uniformly spaced, i.e., the known elevator could accommodate only one size film frame.

[0054] In accordance with the present invention however, the film frames 162 are mounted in respective carriers 166 which, in turn, are mounted in the slot pairs 112, 112. A variety of carriers 166 can be made available which are of identical outer size and shape, whereby all carriers fit in the elevator. However, the carriers are provided with different size holes to accommodate respective different size film frames. Consequently, different size wafers can be provided in the elevator to enable dies from different wafers to be fed to a common semiconductor package.

[0055] The film frame 162 and the carrier plate 168 are preferably formed of metal, although any suitably rigid material could be used.

[0056] It is necessary to be able to displace each carrier 166 to a working position in the pick and place section B. To that end, the attachment 174 of each carrier includes a pair of horizontal gripping pins 192 formed at respective ends of a cavity 193 formed in an edge of the carrier. The pins 192, which face one another in mutual alignment, serve to be engaged by a pulling mechanism for moving the carrier into the pick and place section, or back into the elevator, as will be explained.

[0057] The pulling mechanism includes a pulling head 200 or Y-beam assembly (see FIGS. 1 and 7) arranged to be moved horizontally by a drive belt 202 (see FIG. 2) which extends around a pair of pulleys 204, 206 that are mounted to the base frame 102 for rotation about respective horizontal axes. By rotating the belt 202, a lower flight 208 thereof will travel toward or away from the elevator 100, depending upon the direction of belt rotation.

[0058] The pulling head 200 includes a clamp 210 at one end thereof which is clamped to the belt lower flight 208, whereby the pulling head 200 moves together with that lower flight.

[0059] Movement of the belt 202 is effected by a reversible electric servo motor 212 which drives a belt 214 that extends around a pulley 216. The pulley 216 is affixed to the axle of the pulley 204 for transmitting rotation from the motor 212 to the pulley 204. The belts 202 and 214, and the pulleys 204, 206 and 216 are preferably of toothed construction in order to establish a positive, non-slip drive transmission.

[0060] A side of the pulling head 200 facing the elevator includes a protruding portion 220 sized to fit within the cavity 193 formed between the gripping pins 192 of the carrier. The protruding portion includes a pair of pull pins 222 that are adapted to be extended or retracted laterally with respect to a direction of travel or first axis Y of the pulling head. A pair of solenoids 224 are provided which effect the lateral extension or retraction of the pull pins 222 which are depicted in a retracted state in FIG. 7.

[0061] The pulling head 200 carries a pair of linear bearings (not shown) at opposite ends thereof which mount the pulling head for sliding movement along lower edges of respective beams 226 of the base frame 102.

[0062] It will be appreciated that by actuating the motor 212 in one direction, the pulling head 200 can be advanced toward the elevator to cause the protruding portion 200 to enter the recess 193 of whichever carrier 162 has been moved by the elevator 100 to a position in alignment with the pulling head 200. By then actuating the solenoids 224, the pulling pins 222 are extended, as shown in FIG. 8, whereupon subsequent sliding movement of the pulling device 200 in the opposite direction along axis Y (in response to a reversing of the motor 212) causes the pulling pins 222 to engage the gripping pins 192 and pull the respective carrier 166 partially out of the elevator 100 and into the pick and place section.

[0063] The pulling head also includes a protruding arm 230 (see FIG. 7) that is adapted to contact a limit switch (FIG. 1) which stops the motor 212 to prevent the pulling head from slamming into the frame.

[0064] Once a film frame and respective wafer has been partially pulled out of the elevator and into the pick and place section, it is supported at one end by the elevator and at another end by the pulling head 200. Then, a transfer mechanism moves the dies in the receiver section C along an X axis oriented perpendicular to the Y axis. The receiver section C can be in the form of a flip station 500 that lowers and inverts the dies. Before describing the pick and place section, the flip station 500 will be described.

[0065] Die Flip Station

[0066] The die flip station 500 is used to receive dies removed from the wafer, invert them, and drop them on a die shuttle for delivery to a main pick and place machine. See FIGS. 9-11.

[0067] The die flip station 500 includes a main frame 502, which is primarily a vertically oriented flat plate. Mounted on the front face of the frame 502 are two parallel tracks 506. A cart 504 is mounted on the tracks 506 with linear bearings for vertical movement along the length of the tracks 506. At the base of the tracks, stops 536 are provided to limit the downward movement of the cart 504. A horizontal bar 538 extends along the top of the tracks 506 to limit the upward vertical movement of the cart 504. A compression spring is mounted between the main frame 502 and the cart 504. The spring positions the cart 504 vertically against the horizontal bar 538 when the drive motor 534 is off. The spring also maintains a preload on the system to ensure proper sequence of operation of the system, as described below.

[0068] The cart 504 includes a rotatable platform 508, which is mounted on the cart 504 by bearings 540.

[0069] As can be seen most clearly in FIGS. 11a-11 d, the platform 508 includes a flat receiving surface 510 and an opposite curved surface 514. At each edge of the receiving surface 510, shoulders 512, 513 are provided.

[0070] A drive mechanism 542 is provided so as to enable the platform to be rotated through 180 degrees and then lowered toward the shuttle with one continuous movement of a drive motor 534. The drive mechanism 542 includes a system of pulleys and drive belts, as will be explained herein below.

[0071] At one end of the rotatable platform 508 is a pulley 516. Adjacent pulleys 518, 520 are mounted on the cart 504 in a location adjacent the platform pulley 516. Additional pulleys 522 and 524 are mounted on an edge of the frame 502 such that the uppermost frame pulley 522 is above the uppermost cart pulley 518 and the lowermost frame pulley 524 is located below the lowermost cart pulley 520. A drive belt 530 is mounted in cooperation with the pulleys 516, 518, 520, 522, 524. See FIGS. 9 and 11.

[0072] In a preferred embodiment, the drive belt 530 includes teeth which engage with at least pulleys 516, 522 and 524. The pulley 516 is rotationally fixed with respect to the rotatable platform 508.

[0073] Pulley 524 is concentrically mounted with a larger pulley 526. In addition, a drive pulley 528 is engaged on a shaft of a drive motor 534. A second drive belt 532 cooperates between pulleys 528 and 526 so as to drive pulley 524.

[0074] In a first receiving position, the cart 504 is at an uppermost position on the tracks 506, and the die receiving platform 508 is oriented with the receiving surface 510 facing directly upward. See FIG. 11a. When the rotating platform 508 and the cart 504 are in this first receiving position, the die flip station 500 may receive dies from the vacuum head. In order to ensure that the dies stay in their intended location on the die receiving surface 510, a plurality of small holes are arranged along the die receiving surface 510. The die receiving platform 508 is hollow and is connected to a source of low negative pressure (vacuum) through port 539. Accordingly, when the die are dropped onto the die receiving surface 510, the vacuum created in the platform 508 pulls air in through the small holes in the die receiving surface 510, which holds the die onto the die receiving surface 510 with a slight suction.

[0075] To deliver the die onto the shuttle below the die flip station 500, the motor 534 is driven in a first direction so that the second drive belt 532 moves in the direction of arrow A, as seen in FIG. 11b. When the belt 532 is driven in the direction of arrow A, the first drive belt 530 is driven in the direction of arrow B by means of the pulleys 526, 524. The drive belt 530 engages with pulley 516 and causes the rotatable platform 508 to rotate in the direction of arrow C. The curved surface 514 of the rotatable platform 508 enables the rotatable platform to rotate with respect to the cart 504. In view of the fact that the pulley 516 is able to rotate, the cart 504 stays stationary with respect to the tracks 506 and the frame 502.

[0076] After the rotatable platform 508 has rotated 180 degrees, the corner 512 contacts the front face 544 of the cart 504. See FIG. 11c.

[0077] After the rotatable platform 508 has rotated a full 180 degrees, the corner 512 of the rotatable platform makes firm contact with the front face 544 of the cart 504. The contact between the corner 512 and the front face 544 prevents further rotation of the rotatable platform 508. See FIG. 11c.

[0078] Once rotation of the rotatable platform 508 is stopped by contact between the shoulder 512 and the front surface 544, the further movement of the first drive belt 530 with respect to the rotatable platform 508 is prevented. Accordingly, the drive belt 530 is essentially locked to the pulley 516 in a fixed position.

[0079] As the motor 534 continues to operate, driving the second drive belt 532 in the direction of arrow A, the first drive belt 530 continues to move in the direction of arrow B. However, because drive pulley 516 is essentially locked, the continued movement of the first drive belt 530 causes the cart 504 to move downwardly along the tracks 506 until the drive motor is commanded to stop or the cart 504 hits the stops 536. Once the cart 504 contacts the stops 536, the drive belt 530 cannot rotate any further and continued motion is not possible.

[0080] As a result of this motion, after the die are placed on the die receiving surface 510, and the motor 534 begins rotation, the die receiving platform 508 rotates through 180 degrees so that the die are held to what is now the downwardly facing die receiving surface 510. Once the platform 508 has rotated through the 180 degree movement so that the die receiving surface 510 is facing downwardly, the die receiving platform 508, together with the cart 504, is moved downwardly toward the shuttle. Once the cart 504 and the die receiving platform 510 are at the lower-most position, as illustrated in FIG. 11d, the vacuum is released from the port 539 so that the die are released onto the shuttle.

[0081] After the die have been released from the die receiving platform 508, the drive motor 534 is operated in the reverse direction. Operation of the drive motor in the reverse direction initially causes the cart 504 to vertically retract along the tracks 506 while drive pulley 516 is locked from rotation until the cart 504 contacts the horizontal bar 538 (up stop). This occurs because of the preload on the system from the spring described previously and is required to occur before rotation of platform 508 or the previously placed die on the shuttle surface would be swept off.

[0082] Continued rotation of the drive motor 534 and drive belt 532 will now rotate drive belt 530 and drive pulley 516 which will allow the receiving platform 508 to rotate 180 degrees in the opposite direction of arrow C so that the die receiving surface 510 is once again facing upwardly. Once the die receiving platform 508 has rotated through 180 degrees, and the die receiving surface 510 is facing upwardly, the shoulder 513 contacts the front face 544 of the cart 504, thus preventing further continued rotation of the die receiving platform 508. Thus, the die flip station 500 is again in its first receiving position with a die receiving surface 510 facing upwardly and the die receiving platform 508 at the top of the tracks 506.

[0083] Thus, when the cart 504 is at the uppermost position, the spring enables the die receiving platform to rotate, prior to lowering the cart 504. And, when the cart 504 is at a lowermost position, the spring enables the cart to be raised prior to rotating the die receiving platform.

[0084] Thus, the die flip station 500 can continue to be cycled between the first die receiving position and the second die delivery position.

[0085] Pick and Place Section

[0086] Vacuum Pick Head Assembly

[0087]FIG. 12 is a perspective view of the overall frame of the wafer handler of the present invention. Most of the functional components are not shown on the frame in this figure so that the drive elements for the vacuum pick head 600 and the die chuck ejector assembly 700 of the transfer mechanism at the pick and place section can be seen.

[0088] Specifically, a mounting plate 602 extends across the front face of the machine. At each end of the mounting plate 602 are pulleys 604, 606. A drive belt 608 is mounted on the pulleys 604, 606.

[0089] Turning attention now to FIG. 13, a back view of the frame of the present invention is illustrated showing the drive means for the vacuum pick head assembly 600 and the die chuck ejector assembly 700. With regard to the drive means for the vacuum pick head assembly, a motor 610 is mounted at a back side of the plate 602. A pulley 612 is mounted on the drive shaft of the motor 610 and is in alignment with a pulley 614, which is also secured to a back side of the plate 602. A belt 616 interconnects the pulley 614 with the pulley 612 of the drive motor 610. The shaft 616 of the pulley 614 extends through the plate 602 and supports the pulley 604, so that rotation of the motor 610 drives the drive belt 608.

[0090] A track 618 is mounted on the front side of the plate 602 parallel to and slightly below the drive belt 608. A plate 620 is slidably mounted on the track 618 by means of linear bearings. In addition, the plate 620 includes a clamp 622 mounted at a top portion thereof. The clamp 622 is secured to the drive belt 608 with screws or other conventional means so that the plate 620 is secured to a fixed location on the drive belt 608. Accordingly, movement of the drive belt 608 moves the plate 620 along the track 618 in the horizontal direction illustrated in FIG. 12, which direction corresponds to the earlier-described X axis.

[0091]FIG. 1, which is a perspective view of the assembly, taken from a similar perspective as FIG. 12, and further illustrates the vacuum pick head assembly 600 and the die ejector assembly 700.

[0092] Turning attention now to FIG. 14, a preferred embodiment of the vacuum pick head assembly 600 is illustrated in further detail. The vacuum pick head assembly 600 includes two vacuum pick head units 622, 624. Each of the pick head units 622, 624 is mounted for vertical movement along respective vertical tracks 626, 628 by means of linear bearings 630, 632. Accordingly, vacuum pick head unit 622 can move vertically along track 626 by means of linear bearing 630 and vacuum pick head unit 624 can move vertically along vertical track 628 by means of linear bearing 632.

[0093] At the top of plate 620 a drive motor 634 is mounted for providing the vertical drive of the vacuum pick head units 622, 624. The drive motor 634 includes a pulley 636 mounted on the drive shaft thereof. A parallel shaft 640 is mounted parallel to the drive shaft 635 of the drive motor 634. The parallel shaft 640 includes a pulley 638 mounted in cooperation with the pulley 636 on the drive motor shaft 635. A belt 650 interconnects the pulley 636 on the motor shaft 635 and the pulley 638 on the parallel shaft 640. Also mounted on the parallel shaft 640 are pulleys 642 and 644. Respective clutches 646, 648 are used to selectively engage and disengage pulleys 642, 644 from the parallel shaft 640. Thus, when the drive motor 634 rotates parallel shaft 640, pulley 642 may be driven by engaging the clutch 646, and the pulley 644 may be driven by engaging the clutch 648.

[0094] At the bottom of the plate 620 are arranged lower pulleys 654, 656, which are mounted in alignment with pulleys 642, 644, respectively. A drive belt 652 interconnects the pulley 642 and the pulley 654, and a drive belt 654 interconnects the pulleys 644 and 656. Thus, by driving the drive motor 634 and engaging the clutch 646, the drive belt 652 may be driven. Similarly, by driving the motor 634 and engaging the clutch 648, the drive belt 654 can be driven. The first vacuum pick head unit 622 is connected to the belt 652 by means of a clamp 658. The second vacuum pick head unit 624 is connected to the belt 654 by means of a clamp 660. Thus, vertical movement of the first vacuum pick head unit 622 can be effected by driving the drive motor 634 in a desired direction and engaging the clutch 646 so that the belt 652 moves to drive the first vacuum pick head unit 622. Similarly, the second vacuum pick head unit 624 can be driven along track 628 in a vertical direction by driving the drive motor 634 and engaging the clutch 648.

[0095] Also mounted on the plate 620 is a camera 662 in cooperation with a lighting unit 664.

[0096] The camera 662 and lighting unit 664 can be used to locate predetermined points on the wafer or wafer frame so that operation of the vacuum pick head assembly can be properly calibrated or zeroed with respect to the position of the wafer. As such, the vacuum pick head assembly can be programmed to the exact location over a die that is intended to be picked up by the vacuum pick head assembly. Any conventional control system can be used to coordinate the camera 662 with the controls of the present invention.

[0097] Once the vacuum pick head unit 662 is above the die that is intended to be removed from the wafer, the aforementioned drive mechanism can be activated so as to lower the vacuum pick head unit 622 to the wafer so that the die can be removed from the wafer film. To assist the removal of the die from the wafer film, the die eject chuck cooperates with the vacuum pick head assembly. A more detailed description of the operation of the die eject chuck and its cooperation with the vacuum pick head assembly will follow.

[0098] After the die has been removed from the wafer film, the drive motor 610 is operated so as to drive the belt 608 and to move the vacuum pick head assembly unit 600 to the left side edge of the machine so that the vacuum pick head unit 600 is in alignment with the die flip station 500. Once the vacuum pick head assembly 600 is in alignment with the die flip station 500, the vacuum on the vacuum pick head unit 622 is released and the die is dropped onto the die receiving platform 510 of the die flip station 500.

[0099] After the die is dropped onto the die flip station 500, the drive motor 610 is operated in reverse so that the vacuum pick head assembly 600 is returned to the working position to pick up another die.

[0100] In one embodiment of the operation of the present invention, a first die can be picked up with the first vacuum pick head unit 622 and a second die can then be immediately thereafter picked up by the second vacuum pick head unit 624. The vacuum pick head assembly 600 with both dies attached thereto is then driven to the left side of the machine wherein both dies are simultaneously dropped onto the die flip station 500.

[0101] In this manner, by limiting movement of the vacuum pick head assembly 600 to X axis movement along the track 618, as well as vertical movement along tracks 626, 628, a simplicity of operation can be had. Thus, by controlling placement of the wafer along the Y axis, it is only necessary to control movement of the vacuum pick head assembly along the X axis.

[0102] In an alternative embodiment, the vacuum pick head assembly 600 may include only one vacuum pick head unit.

[0103] In addition, in alternative embodiments, other forms of driving the vacuum pick head units may be used besides the belt drive method disclosed herein. For example, a lead screw and ball nut assembly can be used to raise and lower the vacuum pick head.

[0104] Furthermore, a source of vacuum may be applied to each of the vacuum pick head units 622, 624 in order to apply suction through the nozzle of the vacuum pick head to the die that is being picked up.

[0105] Each vacuum pick head unit 622, 624 includes a nozzle 666, 668, respectively at the lower tip thereof. The nozzle is the part of the vacuum pick head unit 622, 624 that makes contact with the die as the die is removed from the wafer. Different types of die may preferably require different types of vacuum nozzles. Accordingly, a nozzle tray 662 is provided on the pulling head 200. See FIG. 1. The nozzle tray 662 includes a plurality of openings 664. A separate, and different size, nozzle may be stored in each of the openings 664. Accordingly, when it is desired to change the nozzle on one or both of the vacuum pick heads 622, 624, the pulling head 200 is moved so that they nozzle tray 662 is in alignment with the vacuum pick head unit assembly 600, and the appropriate vacuum pick head unit may be lowered down to drop off the existing nozzle in one of the openings 664 and then to pick up a new nozzle from a different one of the openings 664.

[0106] Die Eject Chuck

[0107] The die eject chuck assembly 700 is illustrated in FIGS. 16 and 17. The assembly 700 includes a plate 702, which can also be seen in FIG. 23, and is mounted to the front face of the machine. The plate 702 is mounted on a track 704 with linear bearings so that it can slide lengthwise along the X axis. Mounted parallel to and below the track 704 is a belt 706 which is mounted on pulleys 708, only one of which can be seen in FIG. 23.

[0108] Turning attention now to FIG. 13, a motor 712 is mounted at the backside of the machine. A pulley 714 on the motor shaft is mounted in alignment with a second pulley 716 that is mounted on a shaft 718. A drive belt 720 connects the pulley 714 and the pulley 718. The pulley shaft 718 extends through to the front of the machine and also supports pulley 708, upon which drive belt 706 is secured. The plate 702 is clamped to the belt 706 so that the plate 702 moves along the track 704 with the belt 706.

[0109] As can be best seen in FIGS. 16 and 17, the die eject chuck assembly 700 includes a plurality of anvils 722, 724, 726, 728. Each of the anvils is mounted on a respective block 730, 732, 734, 736 which move up and down along tracks 776, 778, 780, 782 with linear bearings.

[0110] Mounted below and in alignment with each of the anvil blocks 730, 732, 734, 736 is a respective needle block 738, 740, 742, 744. A shaft 784, 786, 788, 790 projects from each of the needle blocks 738, 740, 742, 744 and extends through the anvil blocks and the anvil itself. At the top of each shaft 784, 786, 788, 790 are a plurality of needles. In a preferred embodiment there are four needles, however, more or less may be used as needed or desired.

[0111] The needle blocks 738, 740, 742, 744 also move vertically along the respective tracks 776, 778, 780, 782.

[0112] At the left of the die eject chuck assembly 700 is a drive motor 762. The drive motor 762 drives a belt 800 which is engaged with clutches 792, 794, 796, 798. Each of the anvils includes a respective lead screw 746, 748, 750, 752 which is rotated when the respective clutch 792, 794, 796, 798 is engaged and the belt 800 is being driven by the motor 762. The head 800, 802, 804, 806 of each lead screw engages with a shelf-like platform on the respective needle block 738, 740, 742, 744. Rotation of the lead screw causes the needle block to be lifted vertically.

[0113] A spring 754, 756, 758, 760 between the needle block and the anvil block causes the needle block to urge the anvil block upwardly when the needle block is moved upwardly by rotation of the respective lead screw.

[0114] After the anvil block 730, 732, 734, 736 moves a predetermined distance, a ledge 766 of the anvil block engages with a corresponding ledge 764 on the plate 702 to prevent further upward movement of the respective anvil 722, 724, 726, 728.

[0115] After further upward movement of the anvil block is arrested by the ledges 766, 764, the spring between the needle block and the anvil block compresses to allow for further upward movement of the respective needle block. The upward movement of the needle block lifts upwardly the respective shaft 784, 786, 788, 790 through the respective anvil 722, 724, 726, 728. The needles at the top of the shaft then project through the needle openings 768, 770, 772, 774 at the center of the respective anvil.

[0116] Accordingly, rotation of the drive motor 762 and engagement of the respective clutch 792, 794, 796, 798 activates the respective anvil so that the anvil is raised a predetermined distance, and then after upward movement of the anvil is stopped, the needles project from the openings in the center of the anvil.

[0117] It will be appreciated that in accordance with the present invention, the pulling head 200 which displaces the film frame carrier from or into the elevator only moves along the Y axis. That is, the need for such a mechanism to also move along the X axis is avoided by the ability of the vacuum pick head assembly and the die eject chuck assembly to move together by different distances along the X axis. Thus, there is no need to enable either the pulling head or the pick up head to move along more than one axis, thereby simplifying the overall design.

[0118] Furthermore, the ability of the die eject chuck to move by different distances along the X axis eliminates the need to move the die chucks when changing from one die chuck size to another. Rather, it is only necessary to position the replacement anvils in a row along the X axis, and move the anvil block along the X axis to pick up a selected die chuck.

[0119] The provision of a flip station that uses a single motor for both lowering and inverting dies, renders the flip station less complicated and less expensive.

[0120] Although only preferred embodiments are specifically illustrated and described herein, it will be appreciated that many modifications and variations of the present invention are possible in light of the above teachings and within the purview of the appended claims without departing from the spirit and intended scope of the invention. 

What is claimed is:
 1. A wafer handling apparatus, comprising: a frame structure forming: a wafer feed section for storing a wafer holder adapted to support a wafer comprised of precut dies, a wafer pick and place section spaced from the wafer feed section along a first axis, and a wafer receiving section spaced from the wafer pick and place section along a second axis crossing the first axis; a holder displacement mechanism arranged for movement between the feed section and the pick and place section for transferring a wafer holder from the feed section to the pick and place section linearly along the first axis; and a transfer mechanism arranged for movement between the pick and place section and the receiving section for picking up and transferring wafer dies from the pick and place section to the receiving section linearly along the second axis, the transfer mechanism being movable by different distances along the second axis for picking up dies arranged adjacent one another at different locations along the second axis.
 2. The wafer handling mechanism according to claim 1, wherein the wafer feed section comprises an elevator movable up and down and arranged to contain a plurality of wafer holders in vertically spaced relationship, and a drive mechanism for moving the elevator up and down to position selected wafer holders in position to be connected to the holder displacement mechanism.
 3. The wafer handling mechanism according to claim 2, wherein the wafer holder includes a carrier and a film frame mounted on the carrier.
 4. The wafer handling mechanism according to claim 3, wherein the carrier comprises: a plate having a hole extending therethrough; at least one clamp for holding the film frame onto the carrier so that a wafer on the film carrier is disposed over the hole in the plate.
 5. A wafer holder for use in a wafer feeding machine, the wafer holder comprising: a film frame adapted to support a film in a stretched condition, which film supports a precut semiconductor wafer; a carrier comprising a plate have a through-hole in a central portion thereof, the carrier further comprising at least one clamp for holding the film frame onto the carrier so that a wafer on the film frame is disposed over the hole in the plate; a connector mounted at one edge of the carrier for enabling the wafer holder to be engaged by the wafer feeding machine.
 6. The wafer holder of claim 5, wherein said plate includes parallel edges adapted to be slidably received in an elevator rack.
 7. The wafer holder of claim 5, wherein the connector comprises a pair of pins in spaced configuration.
 8. The wafer holder of claim 7, wherein the at least one clamp comprises a spring clip.
 10. A wafer feed mechanism in an apparatus for handling semiconductor wafers, the wafer feed mechanism comprising: an elevator movable up and down in a frame; a plurality of wafer carriers mounted in the elevator in vertically spaced-apart relationship, the wafer carriers being slidable into and from the elevator in a horizontal direction; a plate-like film frame mounted on each wafer carrier, the film frame forming an aperture, and including a film extending across the aperture; and a precut semiconductor wafer mounted on the film of each film frame.
 11. The wafer feed mechanism of claim 10, wherein the carrier comprises: a plate having a hole extending therethrough; a recess formed adjacent one end of the plate, the recess disposed parallel to the plate and opening toward the hole, the recess receiving a first edge portion of the film frame; a plurality of removable positioning pins extending into the recess and mating with respective positioning notches formed in the first edge portion of the film frame; and a hold-down structure mounted on the plate to one side of the hole disposed opposite to the recess for holding a second portion of the film frame.
 12. The wafer feed mechanism according to claim 11, wherein some of the film frames have different size apertures formed therethrough, and at least some of the carriers having different sized holes formed therethrough to conform to the sizes of the apertures of the respective film frames.
 13. A method of feeding semiconductor wafers comprising the steps of: A. seating the wafers on respective film frames, each film frame having an aperture and a film extending across the aperture for supporting the respective wafer, the apertures of at least some of the film frames being of different size from the apertures of others of the film frames; B. mounting the film frames on respective carriers, each carrier having a hole sized in accordance with the size of the aperture of the respective film frame, the hole of each carrier being aligned with the aperture of the respective film frame; C. positioning the carriers in vertically spaced relationship in respective support seats of a vertically movable elevator, each of the carriers configured to be received in any of the support seats; and D. selectively raising and lowering the elevator to bring a selected carrier to an elevation suitable for being removed from the elevator.
 14. The method according to claim 13 wherein step B includes sliding a first edge portion of each film frame into a recess disposed on the carrier while causing notches formed in the first edge portion to mate with positioning pins extending into the recess, and applying hold-down elements to a second side of the film frame disposed.
 15. A wafer feeder, comprising: a main frame; a wafer holder adapted to support a wafer including a plurality of precut dies; a die flip station that includes a track and a pivotable platform slidably mounted on the track, the die flip station being mounted adjacent the wafer holder; a pick-up head located so as to pick up a die from the wafer and drop the die onto the pivotable platform of the die flip station; and a controller for controlling the die flip station so as to pivot the pivotable platform whereby the die can be dropped from the pivotable platform onto an adjacent surface; wherein the die flip station includes a single drive for both pivoting the pivotable platform and for moving the pivotable platform linearly along the track.
 16. The wafer feeder of claim 15, wherein the single drive is a belt drive.
 17. The wafer feeder of claim 15, wherein when the pivotable platform is in a first receiving orientation and at a first receiving position on the track, movement of the drive in a first direction causes the pivotable platform to pivot to a dropping orientation.
 18. The wafer feeder of claim 17, wherein when the pivotable platform is in the dropping orientation at the first receiving position on the track, movement of the drive in the first direction causes the pivotable platform to move linearly along the track.
 19. The wafer feeder of claim 18, wherein the die flip station includes a slide frame that is slidably mounted on the track, and the pivotable platform is pivotably mounted to the slide frame.
 20. The wafer feeder of claim 19, further comprising a shuttle below the die flip station, wherein the adjacent surface is on the shuttle.
 21. A wafer handling apparatus, comprising: a frame structure forming: a wafer feed section for storing a wafer holder adapted to support a wafer comprised of precut dies, a wafer pick and place section spaced from the wafer feed section along a first axis, and a wafer receiving section spaced from the wafer pick and place section along a second axis crossing the first axis; a holder displacement mechanism arranged for movement between the wafer feed section and the wafer pick and place section for transferring a wafer holder from the feed section to the pick and place section linearly along the first axis; and a transfer mechanism arranged for movement between the wafer pick and place section and the wafer receiving section for picking up and transferring wafer dies from the wafer pick and place section to the wafer receiving section linearly along the second axis; the transfer mechanism including a pick up head and a plurality of anvils arranged on a frame along the second axis, the frame being selectively movable along the second axis so that a selected one of the plurality of anvils can be coordinated with the pick up head to pick up dies from the wafer.
 22. A wafer handling apparatus, comprising: a wafer feed section for storing a wafer holder adapted to support a wafer comprised of precut dies, a wafer pick and place section spaced from the wafer feed section along a first axis, and a wafer receiving section spaced from the wafer pick and place section along a second axis crossing the first axis; a displacement mechanism arranged for movement between the wafer feed section and the wafer pick and place section for transferring a wafer holder from the wafer feed section to the wafer pick and place section linearly along the first axis; a pick up head movable along the second axis for picking up dies from the wafer at an adjustable pick up location and delivering the dies to the wafer receiving section; and a die eject chuck movable along the second axis in concert with the pick up head for cooperating with the pick up head in picking up dies from the wafer; wherein the pick up location can be adjusted along the second axis by moving the pick up head and the die eject chuck along the second axis.
 23. The wafer handling apparatus of claim 22, wherein a plurality of dies arranged adjacent one another along the second axis can be picked up without moving the wafer by moving the pick up head and the die eject chuck along the second axis.
 24. A wafer handling apparatus, comprising: a wafer feed section for storing a wafer holder adapted to support a wafer comprised of precut dies, a wafer pick and place section spaced from the wafer feed section along a first axis, and a wafer receiving section spaced from the wafer pick and place section along a second axis crossing the first axis; a displacement mechanism arranged for movement between the wafer feed section and the wafer pick and place section for transferring a wafer holder from the wafer feed section to the wafer pick and place section linearly along the first axis; a pick up head for picking up dies from the wafer and delivering the dies to the wafer receiving section; and a plurality of die eject chucks extending along the second axis, wherein a selected one of the plurality of die eject chucks can be aligned with the pick up head so as to pick up a die from the wafer.
 25. The wafer handling apparatus of claim 24, wherein the pick up head is movable along the second axis and the plurality of die eject chucks are movable along the second axis in concert with the pick up head for cooperating with the pick up head in picking up the die from the wafer. 